104 



Sir J. B. Lawes and Prof. J. H. Gilbert. [Jan. 9, 



graphs of the roots of pots 1, 3, and 4, clearly illustrate this. It is 

 further seen that, in pot 1, without soil-extract, the main roots 

 descended some distance before they threw out any considerable 

 amount of root-branches and of root-fibre ; whereas, in pots 2 and 3, 

 with soil-extract, there was characteristically much more fibre dis- 

 tributed both in the upper layers and throughout the pot. 



It is specially to be noted that, whereas in pot 1 in 1888, with 

 impure and non-sterilised sand, there was a considerable develop- 

 ment of nodules, now in the pure and sterilised sand, not a nodule 

 was observable. 



In pot 2, with soil-extract, one plant was very much larger than 

 the other, and developed very much more root. The smaller plant 

 had, however, several nodules on the main root, near the surface of 

 the soil, and a good many small ones distributed along the fibres. 

 Most of the nodules were more or less shrivelled. The larger plant 

 had a large cluster of nodules on the main root, very near the surface ; 

 and a very large number of single nodules, mostly small, was distri- 

 buted on the root-fibres, quite to the bottom of the pot. Upon the 

 whole those on the larger plaut were less shrivelled. 



In pot 3, also with soil-extract, the main roots extended to, and 

 along, the bottom of the pot ; throwing off mauy side branches, with 

 a very large quantity of fine fibrous root. The greatest distribution 

 was, however, in the upper few inches of the soil. There were two 

 clusters of nodules on one of the plants, and three on the other, 

 besides smaller bunches. A large number of mostly single small 

 nodules was also distributed along the roots. On one of the plants, 

 the largest cluster was on the main root, and on the other the clusters 

 were on the side branches. 



In pot 4, with the garden soil, there was a dense mass of root-fibre 

 throughout the first 6 inches of depth. There were numerous 

 nodules, the majority single, and within the upper 2 or 3 inches of 

 soil. There were also a few small bunches. 



Thus, then, the limited growth in pot 1, without soil-extract, is 

 coincident with the entire absence of nodule-formation ; and the in- 

 creased growth in pots 2 and 3, with soil -extract, is coincident with a 

 very great development of nodules. In pot 4, with garden soil, 

 itself supplying abundance of nitrogen, there was also a considerable 

 development of nodules, but distinctly less than in pots 2 and 3, with 

 soil extract only. 



The vetches were taken up on October 26. They had been photo- 

 graphed on August 3, August 20, September 27, and lastly on 

 October 25, that is, the day before taking up ; and of this last repre- 

 sentation an enlargement w r as exhibited. 



Here, as with the peas, the plants in pots 2 and 3, with soil- 

 extract, had shown more growth than those in pot I without it, before 



